Case report
Absence of left circumflex coronary artery: case report and minireview

Introduction

Absence of the left circumflex coronary artery (LCX) is a very rare coronary anomaly. The anomaly has been reported in only 0.003% of all patients who underwent routine coronary angiography [1]. Although rare, the failure to visualize a coronary artery in its expected anatomical location might cause life-threatening complications such as total occlusion with acute coronary syndromes.

In the present paper, we report a patient with absent LCX and discuss the previously reported cases in terms of diagnostic and clinical importance, association with atherosclerosis and other anomalies.

Case report

A 48-year-old woman was admitted to our hospital with atypical precordial chest pain for 2 years. Because the treadmill exercise stress test was positive, she underwent coronary angiography. On coronary angiography, the left coronary arteriogram showed only one artery arising from the left sinus of Valsalva and continuing as a single left anterior descending coronary artery (LAD) which gave off a large diagonal branch for the left ventricular lateral wall (dual LAD) (Fig. 1). No LCX was seen with a left injection after several different views with repeated coronary angiograms. Then selective right coronary angiography revealed a superdominant right coronary artery (RCA) which crossed the crux of the heart and ascended into the atrioventricular groove, perfusing the posterolateral and lateral walls of the left ventricle (Fig. 1). There were no critical lesions in the coronary arteries. An aortic root arteriography was performed to reveal whether there was evidence of the LCX from any separate origin, but it verified the absence of LCX. Because the treadmill exercise stress test was positive, we performed dobutamine stress echocardiographic examination to prove/exclude ischaemia and it was completely normal.

Discussion

Like double RCA, absence of the LCX is very rare in the literature, with a frequency of 0.003% in all patients who underwent routine coronary angiography [1-5]. Absence of the LCX is usually associated with a large “super-dominant” RCA whose well-developed postero-lateral branches cross the crux of the heart ascending to the left atrioventricular groove and perfuse the zone extending to the LCX territories (Fig. 1). Moreover, the LAD’s well-developed branches (like the present case) or dual LAD may contribute blood supply to the absent LCX territories. These compensating mechanisms prevent myocardial ischaemia and therefore this anomaly is generally accepted as a benign condition unless an atherosclerotic process is superimposed.

We searched MEDLINE (www.ncbi.nlm.nih.gov) for cases of absent LCX and found that so far absence of LCX has been reported 27 times and in 32 cases [6-31]. Here in this case report and minireview we discuss the characteristics of the present case and previous 32 cases with absence of LCX (Table 1). The majority of the patients were over 30 years old at the time of diagnosis and the condition is more common in females.

Hashimoto et al. reported absence of LCX associated with acute anterior myocardial infarction [6]. Percutaneous coronary intervention has been successfully performed to complete occlusion of the left main trunk. If patients undergo emergency coronary angiography, coronary arteries should be quickly and correctly evaluated in order to apply the best treatment modality. An unusually long left main coronary artery or super-dominant right coronary artery may be a clue for absence of LCX. Sato et al. reported an RCA critical lesion with absence of LCX [12]. This condition should be evaluated as equivalent to two-vessel disease including both the RCA and LCX.

Cases of absence of LCX have been sporadically reported during routine coronary angiography. Bestetti et al. found absence of LCX with idiopathic dilated cardiomyopathy in autopsy [15]. These conditions may be accepted to co-exist by chance. On the other hand, Coppi et al. speculated that thoracic large vessel anomalies might be associated with this anomaly [18]. Some authors suggest that multidetector computed tomography should be used in diagnosis of this rare coronary anomaly. Liu et al. reported the case of a 17-year-old girl in whom the clinical diagnosis was absence of LCX by multidetector computed tomography [9]. It may be especially an alternative imaging modality to coronary angiography if patients are young or have atypical chest pain. It is also a safe, non-invasive, cost-effective and fast imaging technique which enables detailed evaluation of coronary arteries.

In conclusion, although absence of LCX is generally considered as a benign entity, it might be atherosclerotic and can cause acute coronary syndromes including myocardial infarction and be associated with other anomalies. Proper diagnosis of absence of LCX is very important because it can be misinterpreted as a totally occluded LCX. In subjects with absent LCX, infarction in the superdominant RCA might be more dangerous. It is more common in females and although conventional coronary angiography is the most widely used diagnostic modality, multidetector computed tomography might also be helpful.

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